In recent years, instead of books printed on paper with ink, so-called electronic books, which circulate as digital data via the Internet, have been wide-spread. The users download and view electronic books using a dedicated electronic book reader or a general-purpose portable terminal or personal computer. Electronic books are also called online books or digital books.
For example, Patent Literature 1 discloses a system for updating the contents of advertisements posted in an electronic book containing body text pages and advertisement pages based on the contents the user has browsed and paid attention to.
On the other hand, in a method of selling an electronic book, the user is allowed to preview a portion or shown sample pages of an electronic book before purchase and if he likes it, the user can purchase the electronic book. This is so-called “browsing” of a digital book.
For example, Patent Literature 2 discloses a system for adding data to an electronic book or updating data in an electronic book based on the operation history while sample pages are browsed.